In the present paper, flowerlike ZnS−ZnO heterogeneous microstructures built up by ZnS-particle-strewn ZnO microrods were successfully obtained at 120 °C for 10 h via a simple one-pot hydrothermal route without the assistance of any surfactant or template, employing S, Zn(CH3COO)2·2H2O, NaOH, and NH3·H2O as reactants. The optical properties of the as-prepared product are different from those of pure ZnO nanocrystals, which were prepared under the same conditions. Meanwhile, the electrochemical research of the products showed that flowerlike ZnS−ZnO heterogeneous microstructures had a strong ability to promote electron transfers between Hb and the Au electrode. The phase and morphologies of the products were characterized by X-ray powder diffraction, transmission electron microscopy, field emission scanning electron microscopy and X-ray energy dispersive spectra.